Benthic shifts in the Cenozoic: preliminary results tracking Atlantic microfossil communities through a changing ocean

This work constitutes part of a project investigating the extent to which marine biota are governed by shifts in environmental conditions, as compared to biotic interactions. Five key periods known for oceanographic change throughout the Cenozoic in the Atlantic Ocean were selected for investigation and sampled from various International Ocean Discovery Program cores (IODP Expeditions 94, 154, 162 and 208).

A suite of micropalaeontological analyses were employed wherein benthic foraminifera (Protista, Rhizaria) and ostracoda (Metazoa, Arthropoda: bivalved crustacea) in the same samples were used to reveal past species diversity, faunal composition, and abundance. Benthic foraminiferal and ostracod biofacies are particularly sensitive to changes in deep-sea environmental conditions, have a rapid turnover and thus are ideal proxies for monitoring biotic responses to marine environmental changes. This information can be combined with lithostratigraphic, geochemical and stable isotope data, and other microfossil data, to gain a robust understanding of past environments.

Here we present preliminary foraminiferal results from three of the most recent of the selected periods (0–0.5; 2.5–3 and 3–3.5 Ma) to elucidate benthic ecosystem conditions for these discrete periods of time, and link them with other Atlantic Cenozoic studies to investigate which environmental variables elicit biotic response and to what extent.